Dolby, Dolby Digital, Dolby Digital Plus, and Dolby E are trademarks of Dolby Laboratories Licensing Corporation. Dolby Laboratories provides proprietary implementations of AC-3 and Enhanced AC-3 (sometimes referred to as E-AC-3) known as Dolby Digital and Dolby Digital Plus, respectively.
Various single-channel and/or multi-channel audio rendering systems such as 5.1, 7.1 or 9.1 multi-channel audio rendering systems are currently in use. The audio rendering systems allow e.g. for the generation of a surround sound originating from 5+1, 7+1 or 9+1 speaker locations, respectively. For an efficient transmission or for an efficient storing of the corresponding single-channel or multi-channel audio signals, audio codec (encoder/decoder) systems such as Dolby Digital (DD) or Dolby Digital Plus (DD+) are being used.
There may be a significant installed base of audio rendering devices which are configured to decode audio signals which have been encoded using a particular audio codec system (e.g. Dolby Digital). The particular audio codec system may be referred to as a second audio codec. The evolution of audio codec systems may lead to an updated audio codec system (e.g. Dolby Digital Plus), which may be referred to as a first audio codec system. The updated audio codec system may provide additional features (e.g. an increased number of channels) and/or improved coding quality. As such, content providers may be inclined to provide their content in accordance with the updated audio codec system.
Nevertheless, a user having an audio rendering device with a decoder of the second audio codec system should still be able to render the audio content which has been encoded in accordance with the first audio codec system. This may be achieved by a converter (e.g., transcoder) which is configured to convert first encoded content (audio content which is encoded in accordance with the first audio codec system) into modified audio content which is encoded in accordance with the second audio codec system (typically by decoding the first encoded content to generate decoded content, and then re-encoding the decoded content in accordance with the second audio codec system). In order to reduce the cost of such converters (which may be implemented within set top boxes), the computational complexity of the conversion should be relatively low. For this purpose, the encoder which operates in accordance with the first audio codec system may be configured to insert one or more control parameters into the bitstream comprising the encoded audio content. The one or more control parameters may be used by the converter to perform the conversion with reduced computational complexity. On the other hand, the generation of the one or more control parameters typically increases the computational complexity of the encoder.
In the present document, methods and systems are described which enable conversion of audio content from a first format (according to a first audio codec system) into a second format (according to a second audio codec system) with reduced computational complexity. The methods and systems described in the present document may be used to reduce the computational complexity at the encoder and/or at the converter.